1. Field of the Invention
The instant disclosure relates to an image capturing system; in particular, to an image capturing system obtaining scene depth information and a focusing method thereof.
2. Description of Related Art
So far the conventional methods of the related art about depth map can be divided into two kinds: 1. making use of the parallax, for example using a 3D camera or array camera to obtain the information of the parallax to obtain calculated the depth information; 2. utilizing an image capturing module having multi apertures to obtain two images with respectively different optical-wavelength bands (for example, two wavelength bands such as visible light and infrared (IR) light), in which each optical-wavelength band corresponds to one aperture, and the information of depth is obtained according to the difference of sharpness between these two images, as described in US Patent Publication 2013/0033579.
Regarding the aforementioned conventional methods of generating the depth map of the related art, the mentioned first method is limited by the length of the baseline and the size of the sensors, such that the depth information of the scene (or the objects in the scene) at near distance cannot be obtained; on the other hand, the mentioned second method is limited by the difference/ratio of sharpness/blur of these two images, thus the depth information at far distance cannot be obtained, meanwhile, degree of blur of the image is approaching to a constant when the distance between the scene and the image capturing module (also called the camera) is increasing or when the focusing point is farther, such that the difference/ratio of sharpness/blur of these two images of the scene at far distance almost does not change with distance, and the depth of the objects at far distance cannot be identified accordingly.